Clean That Coin

Scripture: Matt 25:14-30

Learning Objectives:

  • Students will review how the servant who hid his master’s money in the ground waspunished, but the ones who used what God gave them were rewarded.
  • Students will learn how acid and pH effects dirt and other substances in order to revealcleaner surfaces.
  • Learning objective #3

Guiding Question: How can acids be used to clean away dirt and revive tarnished metals?


3-5 tarnished/dirty pennies (one for each liquid) Note: pennies need to be old with a dull color and not just have dirt on them.

3-5 safe liquids including water, some acids:, lemon juice, hot sauce vinegar, etc., and some bases: baking soda solution

Paper/ paper plate to place the pennies on and label

Pen for labeling and listing hypothesis

Procedure: Review the parable of the Talents including how each of the servants/slaves treated their master’s resources differently. Emphasize how we are to take good care of and use both our physical resources and spiritual talents/abilities. Tell students that in Biblical times, a talent was a very valuable sum that could take several years for a typical worker to earn. Though a talent was not any certain coin, it was a measurement of weight for currency. Make connections between the metals you know and the types of metals found in common coins. Show students some dirty coins. Brainstorm methods of cleaning the coins. Show students a variety of liquids that might help clean the coins. Include water, and both basic and acidic liquids. Make a hypothesis by listing which liquids students think will be better at cleaning the coin. Ask students for their reasons. Ask them if the acidity of a liquid will have an effect. Test each of the liquids. Place the pennies on a piece of paper or plate and label each. Observe the changes and discuss the conclusion.

Additional Questions:

  • Can you hypothesize which liquids might be more or less acidic based on how well they cleaned the penny?
  • What other substances could you try? Howe well do you think it would work in comparison to the substances we tested?

Supplemental Activity: Have students research other properties of acids. Based on these additional properties, have kids keep a list of other everyday items that they think are acidic. Have them bring the item or the name of the item. Students can then create a spectrum of acidity. Explain that acidic substances have a low pH and number on the scale, but more basic substances have a high pH and number. Water is neutral at 7.

Written by: Savannah Negas

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